Test tube closure



March 5, 1968 UD TEST TUBE CLOSURE Filed April 26, 1967 PRioR ART INVENTQR. Friedrich LUDI his A'H'orney United States Patent 3,371,810 TEST TUBE CLOSURE Friedrich Liidi, Flawil, Switzerland, assignor to Ludi 8i Cie, AG., Flawil, Switzerland Filed Apr. 26, 1967, Ser. No. 633,776 Claims priority, application Austria, Apr. 28, 1966, A 4,005/ 66 7 Claims. ('Cl. 21538) ABSTRACT OF THE DISCLOSURE A test tube closure for releasably maintaining a closure at the open end of a test tube. The closure includes a hollow cap having a transverse end Wall for engaging the test tube at its open end, and the cap has a tubular wall extending axially from the periphery of the end Wall and surrounding, with clearance, the exterior of the.

test tube at the region of the open end thereof. An elongated spring strip is situated within the tubular wall of the cap between the latter and the test tube, and this spring strip has a pair of opposed side edges which are axially spaced in the tubular wall of the cap so that one of these side edges is nearer to the end Wall of the cap than the'other of the side edges. This spring strip is formed with a series of axially extending slots situated between its opposed side edges and terminating short of these opposed side edges so as to provide the spring strip between the slots with elongated springy wall portions spaced from each other by the slots of the spring strip. These springy wall portions of the spring strip are curved inwardly away from the outer tubular wall of the hollow cap and the springy wall portions have crests provided with inner surfaces directed inwardly away from the tubular wall of the cap and adapted to resiliently engage the exterior surface of the test tube for resiliently holding the cap thereon.

Background 0 the invention The present invention relates to closures for test tubes.

In particular, the present invention relates to a closure of this type which includes a hollow cap and a springy structure therein, situated at the inner surface of a tubular wall of the cap so as to maintain the latter resiliently on the test tube.

Closure of this general type are used in particular with test tubes which are used primarily for bacteriological investigations. Known closures of this type have above all the disadvantage of scratching the test tube, and in addition these known structures are relatively heavy and expensive.

Summary of the invention It is accordingly a primary object of the present invention to provide a test tube closure which will avoid the above drawbacks.

Thus, it is an object of the present invention to provide a test tube closure which will reliably be maintained on the test tube while at the same time avoiding scratching thereof, being of a relatively light weight, and also being relatively inexpensive.

In accordance with the present invention the closure includes a hollow cap having a transverse end wall for engaging the test tube at its open end and a tubular wall projecting from this end wall and surrounding the test tube with clearance at the region of its open end. Within the hollow cap, extending circumferentially along the inner surface of its tubular wall, is a rolled spring strip of the invention, this strip having opposed side edges axially spaced along the tubular wall of the cap so that one of these side edges is nearer to the end wall of the 3,371,810 Patented Mar. 5, 1968 "ice cap than the other of the side edges. Between its side edges the spring strip is formed with a plurality of axially extending slots which terminate short of the opposed side edges and which define between themselves elongated narrow springy walls. These walls are curved Brief description of the drawings The invention is illustrated by way of example in the accompanying drawings which form part of this ap plication and in which:

FIG. 1 shows a test tube in elevation and shows a closure of the invention, in a longitudinal sectional elevation, mounted on the test tube;

FIG. 2 is a fragmentary side elevation of a spring strip of the invention, shown developed in FIG. 2;

FIG. 3 is a transverse section of the structure of FIG. 2 taken along line IIIIII of FIG. 2 in. the direction of the arrows;

FIG. 4 is a fragmentary, developed side elevation of a known spring structure forming part of a known test tube closure; and

FIG. 5 is a tnansverse section taken along lines V-V of FIG. 4 in the direction of the arrows.

Description of preferred embodiments Referring now to FIG. I, the illustrated test tube closure of the invention includes only a closure cap 1 and a spring strip 2 situated therein, and this assembly is adapted to be placed on the test tube 3 in the manner shown in FIG. 1. The closure cap 1 has a transverse end wall 5 which is adapted to engage the test tube at its open end, and extending from the periphery of the end wall 5 of the cap is a tubular wall 4, which surrounds the test tube with clearance at the region of the open end of the test tube. This tubular wall 4 is cylindrical. The closure also includes an elongated, manually engageable member 6 forming a handle and projecting from the transverse wall 5 in a direction opposite to that in which the tubular wall 4 projects. This handle 6 extends centrally from the transverse wall 5. The transverse wall 5 as well asthe tubular wall 4 and the handle 6 of the cap 1 are all formed from a single body of material so that all of these components 46 are integral with each other.

The tubular wall 4 is formed with a pair of exterior, annular V-shaped grooves 7 which form at the interior of the tubular wall 4- a pair of inner annular ribs which are axially spaced from each other at the interior of the tubular wall 4.

The one-piece cap 1 can be drawn, pressed, or manufactured by injection molding. After it is: drawn, pressed, or injection molded, the grooves 7 are rolled into the exterior surface of the tubular wall 4 of the cap 1, thus providing it with the inner circumferential ribs which are axially spaced from each other along the interior of the tubular wall 4.

In accordance with the invention there is situated within the cap 4 an elongated spring strip 2, which is held between the inner ribs formed by the exterior grooves 7. The radial dimensions of the cap 1 and the test tube 3 are illustrated at an exaggerated scale in the drawing so as to show the structure of the invention more clearly. It is possible to elminate the upper groove 7 and the inner rib formed thereby and tolocate the spring strip 2 at a certain clearance or play may remain between the inner ribs and the spring strip 2 or between the cap end wall 5 and the spring strip 2 in the event that the upper groove 7 is not used.

As may be seen from FIGS. 2 and 3, the elongated spring strip 2 is formed from a rectangular, relatively thin spring sheet having a pair of opposed side edges 3 which extends circumferentially along the interior of the tubular wall 4 of the cap 1. A series of equidist-antly spaced slots 9 are respectively formed between and terminate short of the side edge portions 8 of the spring strip 2, these slots 9 extending axially with respect to the tubular wall 4 of the cap. As a result of these equidistant slots 9, the strip 2 is provided with the elongated narrow springy wall portions 10 which extend between the side edge portions 8, and these wall portions 10 are also equidistant from each other. The narrow springy wall portions 10 of the spring strip are curved inwardly from the plane in which they were initially located so as to project inwardly from the wall 4 of the cap 1, and the inwardly curved wall portions 10 have crests 11 and 11 which are slightly rounded. Thus, with this construction only the side edge portions 8 of the strip 2 remain in the plane in which the wall portions 10 were initially located. The crests 11' and 11" have inner surfaces directed inwardly away from the wall 4 and adapted to resiliently and elastically engage the exterior surface of the test tube 3 for retaining the cap 1 thereon. As is apparent from FIGS. 1-3, alternate elongated wall portions 1d have their crests, such as the crests 11", situated at one predetermined distance from the upper side edge 8, as viewed in FIGS. 13, while the remaining wall portions 10 have their crests 11 situated at a different distance from the upper side edge portion 8 of the spring strip 2. As a result, the successive elastic wall portions 10 have their crests 11 and 11" respectively engaging the exterior surface of the test tube at different axial locations therealong.

Thus, once the spring strip 2 is given the configuration shown in FIGS. 2 and 3, it is rolled into the configuration of a cylinder so that the crests 11' and 11" are directed inwardly toward the axis of the cylinder. Then the rolled, cylindrical, springy strip 2 is inserted into the tubular wall 4 with its side edge portions 8 respectively located between and adjacent the ribs formed by the exterior grooves 7.

When the closure of the invention is mounted on the test tube 3, the exterior diameter of which is somewhat greater than the diameter of a circle to which the crests 11 are tangent and the diameter of an equal circle to which the crests 11" are tangent, the elongated springy wall portions 10 of the strip 2 will elastically yield so that the test tube 3 is gently and smoothly gripped by the springy wall potrions 10 which serve to retain the cap 1 reliably on the test tube 3.

In order to demonstrate the advantages of the abovedescribed structure of the invention, FIGS. 4 and 5 show a springy strip 12 used in a known test tube closure in a manner similar to the springy strip 2 with the closure illustrated in FIG. 1. The springy strip 12 is also formed from a rectangular strip of springy metal. However, in this case tongues 13 are struck from the strip 12 and are deflected to one side thereof from the plane in which they were initially located so that they are curved and apparent from FIG. 5. When this spring strip 12 is rolled project from the strip 12 in a manner which is most clearly and situated in a cap similar to the cap 1, the free ends 14 of the tongues 13 will press against the exterior surface of the test tube 3 when the latter is introduced into the closure. Inasmuch as the springy Wall portion 4 of the strip 2 of the present invention are on the one hand thinner than the tongues 13 and on the other hand are supported at both of their ends by being connected at both of these ends to the opposed side edge portions 8, there is a softer spring action and thus a gentier sliding of the closure of the invention than in the cat: of the springy member 12 which will provide an undesired vibration upon removal of the closure from the test tube, whereas this undesirable vibratory motion is substantially reduced with the structure of the invention upon removal of the closure of the invention from the test tube. Inasmuch as the springy wall portions of the structure of the present invention have no free ends, there is no danger of scratching the test tube. Furthermore, the tongues 13 which are connected at only one end to the strip 12 will fatigue much quicker than the wall portions 10 which are connected at both ends to the remainder of the strip 2, so that the holding force which can be achieved by way of the tongues 13 will be lost after a relatively short period of use of the structure of FIGS. 4 and 5, whereas the holding force achieved by way of the structure of the present invention will be retained over a much longer period of time, and in many cases indefinitely.

It should furthermore be noted that with the known closures the cap is not made of a single body of material. Thus, with the known closures the element which corresponds to the handle 6 is fixed to the cap after the latter is formed. Furthermore, the tubular wall of the known cap, corresponding to the wall 4, is provided at the region Where the spring strip is located with an exterior diameter greater than the diameter of this tubular wall above and below the spring strip, because, in order to achieve a sufl icient holding force with the spring structure 12, more space x is required than in the case of the spring strip 2 of the invention, so that a spring strip 12 cannot simply be held between a pair of inner ribs; such as those formed by the exterior grooves 7, but instead it is essential to provide the cap with an interior diameter at its tubular wall which is enlarged for the purpose of receiving the spring structure 12. As a result the cap 1 of the present invention, and in fact the entire closure assembly shown in FIG. 1, is considerably smaller, lighter, more serviceable, more comfortable to handle, and more economical to manufacture than the known closures.

It is not essential that the cap 1 be made of metal, and it is possible instead to use not only for the cap 1 but also for the spring strip 2 another material such as a suitable plastic.

What is claimed is:

1. A test tube closure comp-risnig a hollow cap having a transverse end wall to be situated over and next to the open end of a test tube and a tubular wall extending from the periphery of said end wall for surrounding a test tube at the region of its open end with clearance, and an elongated spring strip extending cimcumferentially along said tubular wall of said cap at the inner surface thereof and having opposed side edge portions also extending cirncumferentially along said tubular wall at the interior thereof and axially spaced one with respect to the other along said tubular wall so that one of said side edge portions of said spring strip is nearer to said end wall than the other of said side edge portions of said spring strip, said spring strip being formed between and terminating short of said edge portions thereof with a series of axially extending slots defining between themselves elongated narrow wall portions of said spring strip which extend axially along said tubular wall of said cap at the interior thereof, and said elongated wall portions of said spring strip being curved inwardly away from said tubular wall of said cap and respectively having distant therefrom crests provided with inner surfaces directed away from said tubular wall of said cap for engaging resiliently the exterior surface of a test tube in order to retain the cap thereon.

2. The combination of claim 1 and wherein said elongated wall portions of said spring strip are equidistant from each other and wherein said crests thereof are arranged with crests of alternate elongated wall portions situated at one axial distance from one of said side edge portions of said spring strip while the crests of the remaining elongated portions of said string strip are situated at a different distance from said one side edge por- 5 tion of said spring strip, whereby successive wall portions of said spring strip resiliently engage the test tube at different eXial locations, respectively.

3. The combination of claim 1 and wherein said tubular wall of said cap has a constant diameter and is formed with an interior circumferential rib engaging an end of said spring strip.

4. The combination of claim 1 and wherein said end Wall and tubular wall of said cap are formed from a single body of sheet material and are integral with each other.

5. The combination of claim 4 and wherein an elongated manually engageable member integral with said end wall of said cap projects therefrom at the exterior of said cap in a direction opposite to that in which said tubular Wall projects from said end Wall of said cap.

6 6. The combination of claim 1 and wherein said crests are rounded.

7. The combination of claim 1 and wherein said tubular Wall is formed at its interior with a pair of axially 5 spaced circumferential ribs between which said spring strip is located.

References Cited UNITED STATES PATENTS 1,666,541 4/1928 Reutter 21538 1,720,835 7/ 1929 Holmdahl 21538 2,287,746 6/ 1942 Morton 21538 JOSEPH R. LECLAIR, Primary Examiner.

15 R. P'ESHOCK, Assistant Examiner. 

